1 / 13

The 1 st and 2 nd tutoring session of CSc2310 Fall, 2012

The 1 st and 2 nd tutoring session of CSc2310 Fall, 2012. Haidong Xue. How to compile and run a java program (in command-line)?. Code:. public class HelloWorld { public static void main(String[] args ) { System. out.println (" Hellow World!"); } }. Output:. Hellow World!.

urvi
Download Presentation

The 1 st and 2 nd tutoring session of CSc2310 Fall, 2012

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. The 1st and 2nd tutoring session of CSc2310Fall, 2012 HaidongXue

  2. How to compile and run a java program (in command-line)? Code: public class HelloWorld { public static void main(String[] args) { System.out.println("Hellow World!"); } } Output: Hellow World!

  3. How to compile and run a java program (in command-line)? public class HelloWorld{ public static void main(String[] args) { System.out.println("Hellow World!"); } } • Install JDK (not JRE) • Compile: javac HelloWorld.java (You will see the bytecode file: HelloWorld.class) • Run: java HelloWorld (not HelloWorld.class here) (All the file names are case-sensitive)

  4. How to compile and run a java program (in command-line)?

  5. Use variables • Each variable has a type • Use a type keyword to declare a variable • In the most recent grammar, you have to initialize the variable with certain value public class Variables { public static void main(String[] args) { String name = "Haydon"; booleanmale = true; double height = 1.76; //meters System.out.println("Hello World!"); System.out.println("I am: " + name); System.out.println("Am I a male: " + male); System.out.println("My height is: " + height); } }

  6. Use variables Code: public class Variables { public static void main(String[] args) { String name = "Haydon"; booleanmale = true; double height = 1.76; //meters System.out.println("Hello World!"); System.out.println("I am: " + name); System.out.println("Am I a male: " + male); System.out.println("My height is: " + height); } } Output: Hello World! I am: Haydon Am I a male: true My height is: 1.76

  7. Use operators • There are many operators, their usage is very similar to their counterparts in mathematics. • E.g.: + Addition - Subtraction * Multiplication / Division • There are also many other operators like: modulus(%), increment(++) and so on

  8. Use operators Code: public class Operators{ public static void main(String[] args) { double radius = 3.5; double area = 3.1415926 * radius * radius; System.out.println("Area: " + area); } } Output: Area: 38.48450935

  9. Use constants • Like a variable, but the value cannot be changed. (You can only initialize it) • It is very useful to replace your “magic numbers” with constants to increase the readability of your code

  10. Use constants public class Operators{ public static void main(String[] args) { double radius = 3.5; double area = 3.1415926 * radius * radius; System.out.println("Area: " + area); } } public class Constants { public static void main(String[] args) { final double PI = 3.1415926; double radius = 3.5; double area = PI * radius * radius; System.out.println("Area: " + area); } } Which one is better?

  11. Use constants • What will happen, if you use “3.2415” as PI at multiple places, and suddenly find out that it should be “3.1415”? • When you read a 2000 line program, what if you see 8.314? • To avoid those pains, coders use constants.

  12. Use methods • Methods are members of classes • You can use the “.” operator to use the public methods public class Methods { public static void main(String[] args) { double value = 2; System.out.println(Math.pow(value, 3)); // System.out.println(Math.sqrt(value)); // System.out.println(Math.round(value)); // round(value) } } 8.0 1.4142135623730951 2

  13. If you have more questions, I will be here till 8:30pm

More Related